94 PHILOSOPHICAL TRANSACTIONS. [aNNO 17Q1. 



covered with a yellow coat, but not glazed, audit indicated 81°. This loosely 

 cohering solid, being pulverized, afforded a whiter powder than James's powder. 



(d) The crucible, with its charge (b), having a cover well luted on it, was 

 again put into the furnace, and the fire raised to almost as great a degree as I was 

 able. This intense heat was kept up above an hour. After cooling, a white 

 hard, solid mass was found within the crucible. On breaking the vessel, to de- 

 tach from it the charge, this solid mass was found as hard as marble, and to have 

 received its figure from the crucible. Its surface was covered with a yellow 

 vitreous coat, and the whole inside of the vessel had a beautiful gold-coloured 

 glaze with many argentine spicula. The pyrometer piece in the middle of the 

 charge was also covered with a fine yellow glaze, and indicated J 66°. This solid 

 hard mass weighed only 21 grs. less than before the experiment, though the 

 whole inside of the crucible was glazed, and had shining spicula on it. A piece 

 of this hard mass being pulverized, it afforded a whiter powder than James's 

 powder is in general. ' 



Exper. 6. 2000 grs. of coarsely powdered antimony, mixed with 1105 grs. of 

 calcined hartshorn in powder, were calcined first in an open vessel, and then ex- 

 posed to a great degree of fire in a close vessel, as in the above experiments with 

 bone shavings, Exper. 3 and 4. The calcination of this mixture in the open 

 vessel afforded '2550* grs. of a less whitish and rather yellowish powder, instead 

 of a light ash-colour, as with bone shavings, Exper. 3 ; and by the 2d, and 

 even repeated exposure to fire, it never could be made quite so white, but seemed 

 more inclined to melt than the powder prepared with unburnt bone. In other 

 respects the effects of fire were apparently the same, or nearly so, as in the ex- 

 yjeriments with bone shavings, Exp. 3, 4 ; for though the loss of weight in th's 

 experiment, reckoning that of the antimony at 29-I- per cent., and that of the 

 bone-ashes at 2^ per cent, should have left 2483 only, instead of 2550; yet in 

 other similar experiments the product corresponded nearer to this calculation, and 

 the loss was sometimes less both of the antimony and bone calcined separately. 

 Some of the persons who prepare the juilvis antimonialis say, that the whitest 

 colour is obtained by first boiling the bone shavings to dissolve their mucilage, 

 and then calcining them with antimony as above shown. Mr. Lile's receipt 

 directs previous decoction of the hartshorn. 



It will not be diflicult, from these experiments, tu give a probable reason for 

 the James's powder being generally of a yellowish cast, and for different parcels 

 of it, as well as of the pulvis antimonialis, being generally of different degrees 

 of whiteness and shades of yellow. The colour of this preparation is however a 



* In another experiment of this kind, 2-1-00 grs. of antimony and 1500 grs. of calcined bone af- 

 forded S+.'iO grs of yellowish hght-brown powder. In a third trial, 0"()0 grs. of antimony and 402 

 grs. of calcined bone gave 850 grs. of yellowish brown powder. — Orig. 



